Head stock device for selective use between the dead center drive and the live center drive

ABSTRACT

In a head stock device for selective use between the dead center drive and the live center drive there are provided a sleeve secured to the head stock, a spindle journalled by the spindle through bearing means, a driven pulley rotatably mounted on the sleeve, a pawl mounted on the spindle to be engageable with the pulley, the pawl, when engaged with the pulley, transmitting the driving torque from the pulley to the spindle, a preload mechanism disposed between the spindle and the sleeve, the preload mechanims including a spring for applying a preload upon the bearing means, and a clamping mechanism including a threaded member secured to the sleeve, an outer clamping member mating the threaded member and moved axially when rotated by an operating handle, and an inner clamping member secured to the spindle and disposed to be engaged by the outer clamping member when the outer clamping member is moved axially in one direction to apply axial pressure upon the spindle thus increasing the preload on the bearing means. The outer and inner clamping members are arranged such that they are disengaged from each other by the rotation of the spindle.

United States Patent Kobayashi HEAD STOCK DEVICE FOR SELECTIVE USE BETWEEN THE DEAD CENTER DRIVE AND THE LIVE CENTER DRIVE Akiyoshi Kohayashi, Kariya, Japan Toyoda Koki Kabushiki Kaisha, Aichi-ken, Japan Filed: March 1, 1971 Appl. No.: 119,497

lnventor:

Assignee:

151 3,681,879 1 Aug. 8, 1972 Primary Examinerl-larold D. Whitehead Attorney-Wenderoth, Lind & Ponack ABSTRACT dle, a preload mechanism disposed between the spin- [30] Foreign Application Priority Dam dle and the sleeve, the preload mechanims including a March 10, 1970 Japan ..4S/22558 spring for applying a preload upon the bearing means, and a clamping mechanism including a threaded [52] US. Cl. ..51/237 R, 82/30 mem e ecu to e sleeve. an outer ping [5|] Int. Cl. ..B24b 41/04 member mating the threaded e be a d mo ed axi- 58 Field Search ..s2/30; 51/237 y when rotated y an Operating handle. n n inn r clamping member secured to the spindle and disposed 5 References Cited to be engaged by the outer clamping member when the outer clamping member is moved axially in one UNITED STATES PATENTS direction to apply axial pressure upon the spindle thus increasing the preload on the bearing means. The ggggg; lshnfingreen outer and inner clamping members are arranged such 894 634 7/l908 H gi dirige lllllllllllllllllll 4 that they are disengaged from each other by the rotae s e e I 01 l 3,145,507 8/1964 Price ..51/237 x sp'nd 3 Claims, 5 Drawing Figures ill V 79a G5 23 mi 15" a l 33* 27a 3 i5" I W I i T b as minim i 221 V H I A v /1,

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sum 3 CF 3 INVENTOR BY wwmmf ATTORNEYS HEAD STOCK DEVICE FOR SELECTIVE USE BETWEEN THE DEAD CENTER DRIVE AND THE LIVE CENTER DRIVE BACKGROUND OF THE INVENTION This invention relates to a head stock device for selective use between dead and live center drives of a spindle of a machine tool, such as a grinding machine.

in the grinding operation with a grinding machine it is usual to use the dead center drive for working a workpiece held by centers and to use the live center drive for working a workpiece having a large center opening or a workpiece held by a chuck. For this reason, in a grinding machine such as a universal grinder adapted to work both inner and outer surfaces of a cylindrical workpiece the head stock of the grind ing machine is constructed such that the drive of the workpiece can be readily switched between the live center drive and the dead center drive.

A switching claw has generally been used to switch the drive between the live center drive and the dead center drive. However, during the dead center drive, since the workpiece is supported by the center of the head stock to receive the grinding or cutting resistance by the center so that high accuracy of the working can not be assured unless the stiffness of the spindle is increased. For this reason it has been the practice to securely fix the spindle to a bearing by means of a knock pin during the dead center drive. Thus the claw is operated to disconnect the spindle from an associated pulley for the dead center drive for coupling together the spindle and the head stock and the knock pin is inserted through the spindle and the head stock for preventing the rotation of the spindle at the time of the dead center drive, whereas at the time of the live center drive the claw is operated to couple together the spindle and pulley and to disconnect the spindle from the head stock and the knock pin mentioned above is removed.

in the arrangement wherein the spindle is secured to the bearing by the knock pin, even when the claw is operated to couple together the spindle and the pulley, when the operator fails to free the spindle from the bearing by removing the knock pin it is impossible to drive the pulley and the spindle by the energization of the driving motor, thus resulting is the burn out thereof or breakage of the intermediate shaft.

SUMMARY OF THE INVENTION It is therefore an object of this invention to provide an improved head stock device for selective use between the dead center drive and the live center drive for a spindle of a machine tool, such as a grinding machine, capable of applying a larger preload on the bearing means supporting a spindle in a sleeve during the dead center drive than during the live center drive thereby increasing the stiffness of the bearing means for improving the working accuracy.

Another object of this invention is to automatically decrease the preload to a suitable preset value for preventing heating of the spindle when the drive is switched from the dead center drive to the live center drive.

Still another object of this invention is to provide an improved head stock device according to which when the drive is switched from the dead center drive to the live center drive the spindle is automatically freed by utilizing the driving power applied thereto thus preventing the heating of the spindle as well as the burn out of the driving motor.

According to this invention, these and further objects can be accomplished by providing a head stock device for selective use between the dead and live center drives for a spindle of a machine tool, comprising a head stock base, a sleeve secured to the head stock base, a spindle journalled by the sleeve through bearing means, a driven pulley rotatably mounted on the sleeve, a pawl mounted on the spindle to be engageable with the pulley, the pawl, when engaged with the pulley, transmitting the driving torque from the pulley to the spindle, a preload mechanism disposed between the spindle and the sleeve and including a spring for applying a preload upon the bearing means, and a clamping mechanism including a threaded member secured to the sleeve, an outer clamping member mating the threaded member and moved axially when rotated by an operating handle, and an inner clamping member secured to the spindle and disposed to be engaged by the outer clamping member when the outer clamping member is moved axially in one direction to apply axial pressure upon the spindle thus increasing the preload on the bearing means, the outer and inner clamping members being arranged such that they are disengaged from each other by the rotation of the spindle.

BRIEF DESCRIPTION OF THE DRAWINGS The invention can be more fully understood from the following detailed description taken in conjunction with the accompanying drawings in which:

FIG. 1 shows a longitudinal section of the novel head stock device when it is utilized for the dead center drive;

FIG. 2 shows a partial longitudinal sectional view of the head stock device shown in FIG. I when it is utilized for the live center drive, and

FIGS. 3, 4 and 5 are cross-sectional views taken along lines lIl-]ll, lV-[V and V-V, respectively, in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the accompanying drawings a preferred embodiment of this invention illustrated therein comprises a head stock base generally designated by a reference numeral 1, a sleeve 2 secured to the inside of the head stock base and a pulley 3 rotatable mounted on the outer end of sleeve 2 by means of bearings 4 and is driven by an electric motor, not shown, through belts 5. An annular ring shaped power transmission member 6 is secured to the outer end of pulley 3, member 6 being formed with a power transmission notch 6a at its outer end. The machine tool further comprises a spindle 7 journalled in sleeve 2 in a manner to be described later, a center 8 fitted in an opening in spindle 7 and a switching pawl or claw 9 pivotally mounted on a pin 10in a recess 7a formed at the outer end of the spindle. During the dead center drive, the pawl 9 is moved into recess away from the power transmission notch 6a, as shown in FIG. 1 whereas during the live center drive, the pawl 9 is rotated 1 from the position for the dead center drive into the power transmission notch 6a, as shown in FIG. 2, for transmitting the driving torque from pulley 3 to spindle 7. Furthermore, as shown in FIG. 1, during the dead center drive, a face plate 11 provided with a dog (not shown) for driving the workpiece is fixedly mounted on the power transmission member 6 and a sealing member 12 is mounted on the outer surface of spindle 7, whereas during the live center drive (the workpiece is held by a chuck l3), face plate 11 and sealing member 12 on the outer surface of spindle 7 are replaced by the chuck 13, as shown in FIG. 2.

As shown in FIG. 1, the outer end and the inner end of spindle 7 are journalled in sleeve 2 by pairs of tapered roller bearings 14a, 14b and 15a, 15b, respectively, which are preloaded by a compression spring 16 interposed between annular rings 17a and 17b. The inner ring 1717 abuts against a nut 18 threadedly secured to spindle 7. Supporting rings 19a and 1% are interposed between outer races of bearings 14a, 14b and 15a, 15b, respectively, the inner races of bearings 15a and 15b abutting against a thrust ring 20 and annular ring 170, respectively. A cylindrical spacer member 21 is interposed between the thrust ring 20 and outer bearing pair 14a and 14b, outer races thereof being positioned by clamping members 220 and 2219.

Thus, the force of the preloading spring 16 urges outwardly the annular ring 17a, inner bearing 15b, supporting ring 19b, inner bearing 15a, thrust ring 20, and spacer member 21 which in turn urges outwardly outer bearings 14a, 14b and ring 190 whereby the outer bearing 14a is urged against a shoulder 7b of the spindle 7 thus preloading tapered roller bearings 15a, 15b, 14a and 14b in each operation of dead and live center drives, the extent of preload applied on these bearings being adjustable by adjusting the force exerted by spring 16.

A threaded cylindrical member 23 is secured to the inner end of sleeve 2 and ring 24 is fixedly mounted on the large diameter portion of the member 23. Stops 25 and 26 are secured on the inner periphery of ring 24 at circumferentially spaced apart points. An outer clamping member 27 is threaded on the reduced diameter inner end of the threaded member 23 and an inner clamping member 28 is connected to the inner end of spindle 7 by means of a key 36, the outer and inner clamping members 27 and 28 being adapted to engage each other through tapered surfaces 27a and 28b. A rotary ring 29 is mounted on the outer clamping member 27, to be free to rotate but not to move axially. As shown in FIG. 5 a handle resetting block 30 and pin 31 are secured to one surface of rotary ring 29. Block 30 and pin 31 are provided for the rotary ring 29 on the opposite sides of the stop 26 and a helical spring 32 is received between stop 25 and block 30. As best shown in FIG. 4, a plurality of projections 29a are formed integrally on the outer end surface of rotary ring 29 to be received in a plurality of recesses 27b formed on the outer periphery of clamping member 27 and compression springs 33 are interposed between cooperating pairs of projections 29a and recesses 27b. The clamping mechanism comprised by rotary ring 29 and clamping members 27 and 28 is covered by a cup shaped cover 34 carrying an operating handle 35 in fixed relation with rotary ring 29.

The head stock device operates as follows: During the live center drive, pawl 9 is projected outwardly of the spindle 7 into notch 6a in the power transmission member 6 secured to pulley 3 and chuck 13 is mounted on the outer end of spindle 7, as shown in FIG. 2. At this time, outer clamping member 27 is moved to the right as viewed in FIG. 1 to disengage its tapered surface 27a from tapered surface 280 of the inner clamping member 28, and pin 31 of rotary ring 29 is urged against stop 25 of the stationary ring 24 by means of spring 32, as shown in FIG. 5. When pulley 3 is driven by the driving motor not shown, the driving torque is transmitted to chuck 13 mounted on spindle through power transmission member 6 and pawl 9, whereby the workpiece, not shown, held by chuck 13 is rotated for working.

To switch the drive from the live center drive described above to the dead center drive, chuck I3 is dismounted from spindle 7 and the pawl 9 is rotated 180 into recess of spindle 7 thus disengaging from the driving power transmission member 6, as shown in FIG. 1. Face plate 11 is fixedly mounted on the power transmission member 6 and the sealing member 12 is mounted on the outer end of spindle 7. Then operating handle 35 is rotated in the counter clockwise direction as viewed from the rear end to rotate rotary ring 29 through cover 34 in the counterclockwise direction as viewed in FIGS. 4 and 5 whereby to rotate in the counterclockwise direction the outer clamping member 27 through recesses 27b in the outer clamping member 27, projections 29a of the rotary ring 29 and compression springs 33 interposed therebetween. Due to the rotation of the outer clamping member 27 relative to threaded member 23, outer clamping member 27 is moved to the left as viewed in FIG. 1 thus engaging its tapered surface 270 against the tapered surface 284 of the inner clamping member 28 secured to spindle 7. The rotary movement of rotary ring 29 is arrested by the engagement of pin 31 against stop 26 thereby compressing spring 32 by plate 30. At the same time, springs 33 are also compressed to further rotate outer clamping member 27 counterclockwise to urge the tapered surface 280 of the inner clamping member 28 to the left as viewed in FIG. 1 by the tapered surface 27a of the outer clamping member 27. Accordingly the inner clamping member 28 applies a force to spindle 7 tending to urge it toward the left so that shoulder 7b applies a force to tapered roller bearing 14b tending to urge it to the left. This increases the preload applied upon bearing 1412. thus increasing the stiffness thereof. The magnitude of the preload on the tapered roller bearing 14b is determined by the repulsive force of the compression spring 33. Under these conditions the workpiece (not shown) is supported between head stock center 8 and the tail stock center, not shown. The workpiece is rotated and worked by the rotation of pulley 3 through power transmission member 6, face plate 1 1 and the dog (not shown) secured to face plate 11. In this manner, during the dead center drive, even when the torque on the workpiece is transmitted to spindle 7 through the head stock center 8, the spindle 7 will not be rotated.

To switch the drive from the dead center drive to the live center drive, face plate 11 is removed from power transmission member 6 and sealing member 12 from spindle 7. Then pawl 9 is engaged with notch 60 of the power transmission member 6 and chuck 13 is mounted on spindle 7 as shown in FIG. 2. Then spindle 7 is rotated in the clockwise direction as viewed in FIGS. 4 and S for separating tapered surfaces 27a and 28a of both clamping members 27 and 28. More particularly, the clockwise rotation of the inner clamping member 28 driven by spindle 7 causes the outer clamping member 27 to rotate also in the clockwise direction under the frictional engagement therebetween and the rotation of the outer clamping member 27 relative to threaded member 23 moves the outer clamping member 27 to the right as viewed in FIG. 1 for separating tapered surfaces 27a and 28a thus releasing the inner clamping member 28 from the pressure toward left as viewed in FIG. 1. The restoring force of spring 32 restores rotary ring 29, cover 34 and operating handle 35 to the position shown in FIG. 5 through block 30. Further, as the pressure applied to inner clamping member 28 is released, the pressure applied to outer bearing 14b urging it toward left is also released whereby the preload on the bearing is reduced.

In this manner, the invention provides a novel head stock device for selective use between the dead center drive and the live center drive, according to which, during the dead center drive, an operating handle is rotated to axially move an outer clamping member by means of screw threads to urge axially an inner clamping member secured to a spindle so as to apply a large preload on bearings supporting the spindle. On the other hand, during the live center drive, the rotation of the spindle automatically releases the spindle from the sleeve or a head stock while at the same time decreases the preload on the bearings to a suitable value. Consequently, the stiffness of the bearings is increased during the dead center drive whereas decreased during the live center drive thus improving the accuracy of the working without the fear of overheating the spindle. Moreover, as the spindle is released by the driving force thereof, the switching device can be operated safely.

Although the invention has been shown and described in terms of a preferred embodiment thereof, it should be understood that many changes and modifications may occur to those skilled in the art without departing from the true spirit and scope of the invention as defined in the appended claims.

What is claimed is:

l. A head stock device for selective use between the dead center drive and the live center drive for a spindle of a machine tool comprising a head stock base, a sleeve secured to said head stock base, a spindle journalled by said sleeve through bearing means, a driven pulley rotatably mounted on said sleeve, a pawl mounted on said spindle to be engageable with said pulley, said pawl, when engaged with said pulley, transmitting the driving torque from said pulley to said spindle, a preload mechanism disposed between said spindle and said sleeve, said preload mechanism including a spring for applying a preload upon said bearing means, and a clamping mechanism including a threaded member secured to said sleeve, an outer clamping member mating said threaded member and moved axially when rotated by an operating handle, and an inner am: at: an srasssssssts flares: outer clamping member is moved axially in one direction to apply axial pressure upon said spindle thus increasing said preload on said bearing means, said outer and inner clamping members being arranged such that they are disengaged from each other by the rotation of said spindle.

2. The head stock device according to claim 1 wherein said outer and inner clamping members are disposed concentrically about said spindle and are provided with cooperating inclined surfaces.

3. The head stock device according to claim 1 wherein said clamping mechanism further comprises a rotary ring connected to said handle and provided with a handle restoring block and a pin, said rotary ring being mounted on said outer clamping member to be free to rotate but not to move axially, a stationary ring including circumferentially spaced apart stops, said pin being positioned in a circumferential groove between said stops, a spring interposed between one of said stops and said block, said rotary ring being formed with a plurality of circumferential projections received in a plurality of recesses of said outer clamping member, and compression springs interposed between respective pairs of said projections and said recesses. 

1. A head stock device for selective use between the dead center drive and the live center drive for a spindle of a machine tool comprising a head stock base, a sleeve secured to said head stock base, a spindle journalled by said sleeve through bearing means, a driven pulley rotatably mounted on said sleeve, a pawl mounted on said spindle to be engageable with said pulley, said pawl, when engaged with said pulley, transmitting the driving torque from said pulley to said spindle, a preload mechanism disposed between said spindle and said sleeve, said preload mechanism including a spring for applying a preload upon said bearing means, and a clamping mechanism including a threaded member secured to said sleeve, an outer clamping member mating said threaded member and moved axially when rotated by an operating handle, and an inner clamping member secured to said spindle and disposed to be engaged by said outer clamping member when the outer clamping member is moved axially in one direction to apply axial pressure upon said spindle thus increasing said preload on said bearing means, said outer and inner clamping members being arranged such that they are disengaged from each other by the rotation of said spindle.
 2. The head stock device according to claim 1 wherein said outer and inner clamping members are disposed concentrically about said spindle and are provided with cooperating inclined surfaces.
 3. The head stock device according to claim 1 wherein said clamping mechanism further comprises a rotary ring connected to said handle and provided with a handle restoring block and a pin, said rotary ring being mounted on said outer clamping member to be free to rotate but not to move axially, a stationary ring including circumferentially spaced apart stops, said pin being positioned in a circumferential groove between said stops, a spring interposed between one of said stops and said block, said rotary ring being formed with a plurality of circumferential projections received in a plurality of recesses of said outer clamping member, and compression springs interposed between respective pairs of said projections and said recesses. 